Guided tissue regeneration plate for use in a process for growing jaw bone in anticipation of performing dental implants

ABSTRACT

A method of growing jaw bone and the related guided-tissue regeneration plate support and fixation system employed in the method where an isolated and protected space free from tissue impingement, occlusal loading, chewing forces or muscular pressure is created between the periosteum and the jaw bone. This space is created by first placing either a dental implant or a guided-tissue regeneration plate support and fixation system tenting-type support screw into the jaw bone. The plate portion of the guided-tissue regeneration plate support and fixation system, preferably made out of titanium, is a two-piece structure including a first support plate component having a peripheral region and a generally open central portion and a fine mesh screen juxtaposed over the central portion of the support plate and fixed to the peripheral region thereof. Alternatively, a titanium blank can be controllably etched to obtain reduced thickness central regions which, along with the original thickness regions, are methodically pierced to obtain numerous apertures to achieve the desired porosity for the central regions and the desired strength and pliability of the peripheral regions. The guided-tissue regeneration plate is either snapped-down onto the head of the support screw or onto a specialized and modified healing screw of a dental implant which has a receiver cap or is screwed directly into a dental implant. The plate is then bent and molded into the proper shape to provide the protected space.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a Continuation-in-Part of U.S. patent application Ser.No. 08/609,870, filed Mar. 1, 1996, by Dane Q. Robinson and entitledMETHOD AND APPARATUS FOR GROWING JAW BONE UTILIZING A GUIDED-TISSUEREGENERATION PLATE SUPPORT AND FIXATION SYSTEM, now U.S. Pat. No.5,839,899.

FIELD OF THE INVENTION

[0002] This invention relates to the art of dentistry and, moreparticularly, to a devices which relate to the surgical placement ofendosseous dental implants in the maxillary or mandibular jaw bone.Still more specifically, this invention relates to the growing of jawbone in order to obtain adequate volume of osseous structure by using athin titanium bone plate/screen which is mated to an underlying supportbone screw or to a dental implant.

BACKGROUND OF THE INVENTION

[0003] The successful placement of endosseous dental implants has beenwell documented for over 30 years; however, the success of theseendosseous dental implants has been limited by the quality and quantityof existing bone a given patient would present with. Due to thedestructive nature of dentures to the underlying jaw bone as well as tothe fact that bone that is not internally stimulated by tooth roots willatrophy, the amount of bone in many people is very limited for theplacement of dental implants, especially for those who have been missingteeth for an extended period of time.

[0004] Bone grafting has become an essential element for the successfultreatment of those who do not have enough bone for dental implants. Asviable methods, blocks of hip bone have been affixed to the jaw, andfreeze-dried demineralized bone protein has been used as a stimulant tocause the patient's bone cells to become active and lay down new boneonto the existing bone areas and into the new bone graft areas. Throughexperience and research, it has become evident that, for bone graftingto be successful, it must be given an isolated space to grow, protectedfrom muscular pressure, tissue impingement and chewing forces. In orderto create this space, many approaches have been proposed. For example,both Syers (U.S. Pat. No. 5,297,563) and Magnusson et al (U.S. Pat. No.4,961,707) teach the use of a fabric-like membrane which is used over abony defect. Although this barrier creates an isolated space from theinvasion of epithelial cells into the bony defect or bone graft area, itdoes not create a protected space from chewing forces or tissuepressure.

[0005] Morgan (U.S. Pat. No. 5,380,328) teaches the use of a compositeperforated titanium mesh layered with polytetrafluoraethylene (PTFE orTeflon®) fibers. Even though this approach would be feasible forcreating a protected space in order to grow bone, it has some severelimitations. This material requires the placement of peripheral bonescrews into the edges of the meshed piece in order to create a directfixation of the titanium mesh to the jaw bone and then bowing-up ortenting-up the center area in order to create the protected space.Often, it would not be feasible to place the peripheral bone screws inthe peripheral areas for fear of damage to the inferior alveolar nervesor sinus penetration or damage to nearby tooth roots. The protrusion ofthese screws above the mesh is also of concern as potentially causing atissue irritation complication with this given procedure.

[0006] Furthermore, the difficulty of forming the exact amount oftenting desired with this material is inherently very difficult tocontrol. Additionally, the removal of this material is complicated bythe need to surgically dissect much deeper to locate the peripheralscrews. This technique would also be expensive and time consuming toemplace due to the need for multiple screws to secure a single mesh.

[0007] On the other hand, as will become more apparent below, theguided-tissue regeneration plate support and fixation systemcontemplated in accordance with the subject invention obtains theability to place a single screw in the center of the bone graft area,thereby facilitating the selection of a screw height that allows for anexact amount of tenting, thus giving the support where it is neededmost. Placement and removal of this device is greatly simplified due tothe fact that peripheral screws are not required (although such can beused). The head of the screw ends up being mostly under the plate, thuspreventing any concern about screw-head irritation or protrusion.Furthermore, concern about damage to neighboring peripheral structuresis eliminated. In general, a much more simplified and cost effectivemethod, apparatus and result are achieved.

[0008] Experience with and further development of the guided-tissueregeneration plate support and fixation system has resulted in animportant advance which enhances its effectiveness in practice. It hasbeen found that the use of a fine mesh screen spanning open areas of aguided-tissue regeneration support plate results in a faster and morecomplete bone regeneration of the underlying bony ridge and faster andmore healthy growth of the overlying periosteum. The fine mesh screencan be fabricated from any suitable material, resorptive ornon-resorptive, and an especially suitable material, especially when atitanium guided-tissue support plate is employed, is fine mesh screentitanium fixed to the support plate by welding, particularly spot orlaser welding, by an adhesive or by sintering the two-piece assembly.Alternatively, a functional equivalent to a fine mesh screen region canbe obtained by substantially reducing the thickness of predeterminedcentral areas of an imperforate titanium (for example) plate and thenperforating the reduced thickness regions with finely spaced apertures.

OBJECTS OF THE INVENTION

[0009] It is therefore a broad object of my invention to provide animproved dental implant system.

[0010] It is a more specific object of my invention o provide animproved dental implant system which is relatively inexpensive tofabricate and use.

[0011] In another aspect, it is an object of my invention to provide adental implant system which is relatively easy to use to obtain highquality results.

SUMMARY OF THE INVENTION

[0012] Briefly, these and other objects of the invention are achieved bya method of growing additional maxillary or mandibular bone in areas ofatrophy and by the use of a related device to accomplish the task. Apliable guided-tissue regeneration plate, which holds it shape afterbeing bent, is employed as a mating component to a support screw or adental implant and is secured to the jaw structure by fixation of theguided-tissue regeneration plate at a predetermined distance above oraway from the surface of the bone to the support screw or dental implantin order to create a supported and protected space between the undersideof the gum tissue and the original bone which is free from muscular andchewing pressure in order to promote bone growth.

[0013] The guided-tissue regeneration plate support and fixation systemcan be mated with a support screw or screws which are tenting screwsdesigned to be mated with and then become intimately a part of theguided-tissue regeneration plate in order to grow bone in the spacecreated by the guided-tissue regeneration plate system prior to implantplacement. Additionally, the guided-tissue regeneration plate system canbe utilized during implant placement by creating space adjacent to adehisced implant by fixation of the guided-tissue regeneration platedirectly to the implant in order to grow bone height or width. Aguided-tissue regeneration plate according to the present invention canalso be used by affixing it to an existing dental implant that has beenpreviously placed and has undergone bone loss in order to regenerate newbone. The guided-tissue regeneration plate support and fixation systemis adapted to be surgically removed after the bone has grown under itssurface at a later uncovering or implant placement surgery. In analternative preferred embodiment which provides particularly successfulresults and which results in faster and better bone regeneration andperiosteum growth, the guided-tissue regeneration plate consists offirst and second integrated components including a first support platecomponent having a peripheral region and a generally open centralportion and a fine mesh screen juxtaposed over the central portion andfixed to the peripheral region thereof. In a functionally equivalentvariant of the alternative preferred embodiment, the guided-tissueregeneration plate is fabricated starting with an imperforate plate (forexample, of titanium) and then reducing the thickness of predeterminedcentral regions of the plate, a step which can be carried out, forexample, by employing a conventional photoresist mask over the plate inconjunction with an acid etch. After the desired thickness of thecentral regions has been obtained, the central regions may be perforatedwith finely spaced apertures using, for example, conventional lasermachining techniques.

DESCRIPTION OF THE DRAWING

[0014] The subject matter of the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,may best be understood by reference to the following description takenin conjunction with the subjoined claims and the accompanying drawing ofwhich:

[0015]FIG. 1 illustrates a bony ridge that has undergone substantialloss;

[0016]FIG. 2 depicts a cross-section of a maxillary midline area of anedentulous ridge showing the original size prior to bone loss;

[0017]FIG. 3 shows the surrounding tissue first reflected away from thebony ridge to expose the ridge in its entirety;

[0018]FIG. 4 depicts the mating of a guided-tissue regeneration platecomponent of the invention to a support screw component of a snap-fitembodiment;

[0019]FIG. 5 shows bone graft material packed beneath the plate andagainst the existing bony ridge;

[0020]FIG. 6 shows how the bony ridge appears after the guided-tissueregeneration plate support and fixation system has been removed toexpose the new bony ridge;

[0021]FIG. 7 depicts the placement of a large implant into the new bonyridge;

[0022]FIG. 8 shows the placement of an implant into an atrophic bonyridge;

[0023]FIG. 9 depicts the installation of a guided-tissue regenerationplate using a screw supplied by an implant manufacturer;

[0024]FIG. 10 illustrates the final result of the process shownprogressively in FIGS. 8, 9 and 10;

[0025]FIG. 11 illustrates the manner in which the guided-tissueregeneration plate can be snap-attached over a modified healing screwmade to internally thread into a dental implant;

[0026]FIG. 12 depicts a non-perforated embodiment of the guided-tissueregeneration plate;

[0027]FIG. 13 illustrates a snap configured support screw ready toreceive a guided-tissue regeneration plate;

[0028]FIG. 14 depicts the guided-tissue regeneration plate over the snapconfigured support screw after the edges have been bent down to create aspace below the guided-tissue regeneration plate;

[0029]FIG. 15 illustrates a perforated version of the guided-tissueregeneration plate;

[0030]FIG. 16 depicts a guided-tissue regeneration plate being securedto a guided-tissue regeneration plate support screw by a small setscrew; and

[0031]FIG. 17 illustrates the manner in which an exemplary healing screwof the sort typically supplied by a dental implant manufacturer can beemployed to secure the guided-tissue regeneration plate to a dentalimplant;

[0032]FIG. 18 shows in plan view a guided tissue regeneration supportplate used in an alternative preferred embodiment of the invention;

[0033]FIG. 19 is a view similar to FIG. 18 illustrating the optional useof stabilizing members added to the central, substantially open regionof the support plate;

[0034]FIG. 20 illustrates a fine mesh screen component used in thealternative preferred embodiment of the invention;

[0035]FIG. 21. show a completed guided tissue regeneration plateaccording to the alternative preferred embodiment of the inventionfabricated by integrating the screen shown in FIG. 20 to the supportplate shown in FIGS. 18 and 19;

[0036]FIG. 22 is a view similar to FIG. 21 illustrating a reinforcedcentral aperture;

[0037]FIG. 23 is an enlarged cross sectional view taken along the lines23-23 of FIG. 22;

[0038]FIG. 24 is a plan view of an imperforate plate used in a variantprocess for preparing the alternative preferred embodiment of theinvention;

[0039]FIG. 25 is a plan view of a mask, overlaying the imperforateplate, used to define predetermined central areas of the imperforateplate to be reduced in thickness;

[0040]FIG. 26 is a plan view of the imperforate plate after thepredetermined central areas have been reduced in thickness; and

[0041]FIG. 27 is a plan view of a completed guided-tissue regenerationplate prepared by the variant process after a perforating step has beencarried out.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The described invention relates to a method of growing jaw boneand to the related guided-tissue regeneration plate support and fixationsystem by which an isolated and protected space free from tissueimpingement, occlusal loading, chewing forces, or muscular pressure iscreated between the periosteum and the jaw bone. This space is createdby first placing either a dental implant or a guided-tissue regenerationplate support and fixation system tenting-type support screw into thejaw bone and then coupling the guided-tissue regeneration plate to thesupport screw.

[0043] The presently preferred embodiment of the support screws,preferably made out of (but not limited to) titanium, are thin shaftedscrews with a relatively high ratio between the greater diameter to theminor diameter of the threads to give the maximum bite and hold into thebone. Preferably, this ratio is at least two. The head of thetenting-type support screw is placed above or away from the bone asuitable distance of the space created in order to grow bone. The screwhead is configured to receive the guided-tissue regeneration plate, thusallowing for most of the head to be either in or under the guided-tissueregeneration plate after it is engaged into a receiver cap of the head.

[0044] In another contemplated embodiment of the support screws, thehead of the support screw is internally axially threaded or is providedwith a threaded or non-threaded well allowing for a pin with a smallhead resembling a micro thumbtack to extend through the guided-tissueregeneration plate into the well and snap or thread into place, therebysecuring the guided-tissue regeneration plate to the head of thetenting-type support screw. The support screw is preferably fabricatedto be very sharp at its tip which includes a self-starting flute inorder to facilitate self-threading for facilitating placement.

[0045] The guided-tissue regeneration plate is preferably made of thintitanium sheet metal having a peripheral thickness of around 5 to 10thousandths of an inch. This thickness allows for the material to bethin enough to be bent into shape, but rigid enough to hold its shapeafter being bent and molded. The present material of choice is Grade 1titanium which is the fully annealed form of titanium advantageouslycharacterized in that it will not spring back after being bent.

[0046] The plates are fabricated with a precise aperture proximate thecenter or wherever needed in order to allow for a precise union andmating to the support screw or receiver cap of the healing screw of adental implant, thus giving a secure fixation, by indirect means, to thejaw bone. The central area of the guided-tissue regeneration plate ispreferably thicker in order to provide more support and rigidity thanthe peripheral region. The combination of the support screw and thethicker area of the plate near the center prevents the guided-tissueregeneration plate from caving-in in the area where maximum support isneeded when overlying pressure, such as muscular pressure, chewingforces, or any other premature loading onto the guided-tissueregeneration plate support and fixation system, is later applied.

[0047] The guided-tissue regeneration plate can optionally be perforatedto allow for better overlying tissue healing as well as to promote theexchange of nutrients and blood supply between the bone graft and theoverlying tissue. Generally, the central, thicker, more supportive areais not perforated to obtain more support. Typically, the number and sizeof the perforations is less concentrated than the amount of solid spaceto create a more supportive plate at a thinner dimension. If acompletely imperforate barrier is desired to isolate all transfer ofunwanted epithelial cells into the bone graft area, then theguided-tissue regeneration plate is fabricated imperforate except forthe generally centrally disposed aperture for fixing the plate to itssupport screw.

[0048] However, if a temporary period of isolation from epithelial cellsis desired to create a membrane barrier from epithelial cells for alimited period of time which allows for the exchange of nutrients, ions,and tissue fluid or perhaps blood supply, then a resorptive barrier suchas Vicryl™, collagen, resorptive hydroxyapatite crystals or Guidor™ canbe applied to the under or over side of the guided-tissue regenerationplate to seal the perforations, then resorbing a limited time laterafter the system is installed.

[0049] If a non-resorptive semi-permeable result is desired, then theperforations can be covered by applying a suitable material such as PTFEfibers. After a period of several months have passed, the entire systemis removed and then the implants are either simultaneously placed duringthis surgery or uncovered by placing healing caps into the implants. Ifthe only desired effect is to create a better ridge for thestabilization of a denture, then the system may be left in placeindefinitely.

[0050] Having now discussed the fundamentals of the present invention,attention is invited to the several FIGS. for an alternative andclarifying disclosure as the discussion proceeds.

[0051]FIG. 1 shows an exemplary existing midline cross-section of amaxillary edentulous ridge which has undergone substantial bone loss.For orientation purposes, landmarks can be identified by the palatalbone 1, the floor of the nose 2, the bony ridge 3, and the gum tissue 4.

[0052]FIG. 2 depicts a cross-section of a maxillary midline area of anedentulous ridge showing the original size prior to bone loss (the gumtissue is not shown in this view). Reference is taken to the marrowspace 5, the cortical bone 6 and the current size of the ridge 7 afterbone loss and to the area of the original size 8 of the ridge prior toatrophy or bone loss.

[0053] Referring now to FIG. 3, in order to place a guided-tissueregeneration plate support and fixation system according to the presentinvention, the tissue is first reflected away from the bony ridge toexpose the ridge in its entirety. The palatal gum tissue 9 is reflected9, the facial gum tissue 10 is reflected, and a guided-tissueregeneration plate support screw 11 is placed into the bony ridge.

[0054]FIG. 4 depicts the mating of the guided-tissue regeneration plate12 to a guided-tissue regeneration support screw 11 of the snap-fitembodiment. (The gum tissue is not shown.) The space 13 is the areawhere new bone will grow, the space having been created by theguided-tissue regeneration plate support and fixation system of theinvention. The guided-tissue regeneration plate support screw 11 isplaced into the bony ridge 3. After the guided-tissue regeneration plate12 is affixed to the guided-tissue regeneration plate support screw 11by snapping it in place, the plate is molded into shape by bending theedges down as shown.

[0055] As shown in FIG. 5, once the guided-tissue regeneration plate 12has been molded into place, then bone graft material 14 is packedbeneath the plate 12 and against the existing bony ridge 3. After aperiod of approximately four-to-eight months, a new bony ridge will formwithin the space created by the guided-tissue regeneration plate supportand fixation system. (Gum tissue not shown.)

[0056] Thus, FIG. 6 shows how the bony ridge appears after theguided-tissue regeneration plate support and fixation system has beenremoved to expose the new bony ridge 15. A small hole 16 remains afterthe removal of the guided-tissue regeneration plate support screw. (Gumtissue not shown.)

[0057]FIG. 7 depicts the placement of a large implant 17 into the newbony ridge. A tooth can be attached to the implant later.

[0058]FIG. 8 shows the placement of an implant 17 into an atrophic bonyridge 3. In this environment, the implant is not fully encased in boneresulting in an exposed area 18 of the implant outside the confines ofthe existing bone 3.

[0059]FIG. 9 depicts the installation of a guided-tissue regenerationplate 12 by inserting the healing screw 19 supplied by the implantmanufacturer which can be used in place of a tenting-type support screwto mate the guided-tissue regeneration plate 12 directly to the implant17. This screw 19 extends through the aperture of the guided-tissueregeneration plate 12 and is thus used instead of the snap-typeembodiment previously described. The space 13 created by theguided-tissue regeneration plate 12 is filled with bone graft material,thus covering the exposed portion of the dental implant 18 which is outof the confines of the existing resorbed bony ridge 3.

[0060]FIG. 10 illustrates the final result of the process shownprogressively in FIGS. 8, 9, 10 after the removal of the guided-tissueregeneration plate (not shown) by revealing that the dental implant 17is now covered with new bone 20 that has grown around the dental implantafter four-to-eight months of healing time and the subsequent removal ofthe guided-tissue regeneration plate system. As will be apparent tothose skilled in the art, after the removal of the guided-tissueregeneration plate, a post has been placed into the dental implant 17 asnormal followed by a crown or tooth 22 which is secured to the post inthe well known manner.

[0061]FIG. 11 illustrates the manner in which the guided-tissueregeneration plate 12 can be snap-attached over a modified healing screw23 made to internally thread into a dental implant 17. The modifiedhealing screw 23 has a receiver cap 24 adapted to receive the generallycentrally disposed aperture in the guided-tissue regeneration plate 12.

[0062]FIG. 12 depicts a non-perforated embodiment 30 of theguided-tissue regeneration plate, particularly illustrating thegenerally central aperture 31 by which the guided-tissue regenerationplate may be secured using a screw as previously described.

[0063]FIG. 13 depicts the snap configured support screw 11 ready toreceive the guided-tissue regeneration plate 30 through the aperture 31.Attention is also directed to the cross-section of the guided-tissueregeneration plate 30 which includes a relatively thick central region32 and a thinner peripheral region 33 as previously described.

[0064]FIG. 14 depicts the mating of the guided-tissue regeneration plate30 over the snap configured support screw 11 after the edges have beenbent down to create the space below the guided-tissue regenerationplate.

[0065]FIG. 15 illustrates a perforated version 35 of the guided-tissueregeneration plate which allows for blood supply to pass freely throughthe plate. Note the generally centrally disposed aperture 25.

[0066]FIG. 16 depicts a guided-tissue regeneration plate 35 beingsecured to a guided-tissue regeneration plate support screw 26 by asmall set screw 27 which is placed through the aperture 25 in theguided-tissue regeneration plate and into the support screw 26 which hasan internally threaded, axially oriented blind hole 36 in its top.

[0067]FIG. 17 illustrates the manner in which an exemplary healing screw19 of the sort typically supplied by a dental implant manufacturer canbe employed to secure the guided-tissue regeneration plate 12 to thedental implant 17.

[0068] While the guided-tissue regeneration plate system described abovehas worked well, experience and further development of the fundamentalconcept has resulted in an alternative preferred embodiment for theguided-tissue regeneration plate component which is discussed below inconjunction with FIGS. 18-21. Thus, referring to FIG. 18, there is showna guided-tissue regeneration support plate 40 which is a first componentof the alternative preferred embodiment for the guided-tissueregeneration plate. The support plate 40 has generally open regions 41,44 defined, in the exemplary configuration, by integral struts 42radiating from a central inner support ring 43 to the main body of thesupport plate. If desired, the central inner support ring 43 and definedspace 44 may be dimensioned and configured to serve the same fixationpurpose as the apertures 31 and 35 in the respective guided-tissueregeneration plates 30, 35 as described above.

[0069] The main body of the support plate 40, i.e., that portion whichis generally outboard the struts 42, the inner support ring 43 and theopen regions 41, 44, is somewhat thicker than the guided-tissueregeneration plates 30, 35 previously described. For example, when thepresently preferred material, titanium, is used, the thickness of thesupport plate 40 may be on the order of 0.008-0.025 of an inch andpreferably about 0.020 of an inch. The material, as noted with respectto the guided-tissue regeneration plates 30, 35, should bebio-compatible, and other metals which are suitable include chromiumcobalt alloy and Teflon-coated surgical steel.

[0070] It will be understood that any suitable configuration of thesupport plate 40 may be employed to provide a peripheral region ofsufficient strength and rigidity as to be readily manually shaped to thecontours necessary to be fitted to the region above the bony ridge of agiven patient as previously described above while providing substantialopen regions 41, 44 surrounded by the peripheral region. However, theconfiguration shown in FIG. 18 has proven to be a good combination ofstrength and intended purpose. Preferably, in order to both increase themoldability of the support plate 40 and to expose the underlying boneand tissue to the passage of nutrients for the additional reasonsdiscussed above with respect to the guided-tissue regeneration plate 35,numerous perforations 45 are provided in the support plate. Because ofthe increased thickness of the support plate 40 in comparison to that ofthe guided-tissue regeneration plate 35, the perforations 45 arepreferably mutually closely spaced consistent with not compromising thestrength of the support plate.

[0071] Referring also to FIG. 19, the struts 42 should be as narrow asreasonably possible while remaining not subject to easy tearing. Forexample, widths for the struts 42 within the range 0.020-0.030 of aninch, and preferably about 0.025 of an inch, are suitable when thepresently preferred material, titanium, is used. Should the centralportion still be somewhat week for the intended purpose (which willbecome more apparent below), one or more supplementary rectangularstruts 48 and/or one or more intermediate, minor struts 46, 47encompassing the center of the support plate may be fixed to the struts42 to provide increased rigidity, either on the upper or lower plane ofthe support plate 40. The widths of the supplementary struts 48 may fallwithin the same range as those of the struts 42 while the widths ordiameters (if titanium wire is used), i.e., the largest transversedimension, of the minor struts 46, 47 may be smaller yet, falling withinthe range 0.010-0.020 of an inch, preferably about 0.015 of an inch. Themethod of fixation of the supplementary strut(s) 47, 47, 48 may be byany suitable expedient such as welding, spot welding, laser welding,adhesive or sintering.

[0072] Attention is now directed to FIG. 20 which shows a secondcomponent of the alternative preferred embodiment for the guided-tissueregeneration plate. This second component is a fine mesh screen 50. Whenthe presently preferred material, titanium, is used, the diameter of thewire may be in the range of about 0.002-0.006 of an inch, and preferablyabout 0.003 of an inch disposed in a fine mesh weave on the order of10×10 wires per inch to 200×200 wires per inch and preferably about50×50 per inch. Referring also to FIG. 21, the fine mesh screen 50 isjuxtaposed onto the support plate 40 generally centrally disposed overthe open areas 41 and fixed in place by any means suitable to thematerial(s) employed. When the presently preferred material, titanium,is used for both components, welding (particularly spot or laserwelding), an adhesive or sintering may be employed. Sintering (i.e.,heating the complete assembly until the titanium components have fusedat the points of abutment) has been found to give particularly goodresults, and, if the supplementary struts 48 and/or minor struts 46, 47are employed, they may be integrated into the structure during the samesintering step.

[0073] When alternative materials, such as chromium cobalt alloy andTeflon-coated surgical steel, are selected, the size parametersdiscussed above for titanium are also suitable, and the fixation of thefine mesh screen 50 to the support plate 40 may be carried out in thesame manner when chromium cobalt alloy is employed. However, whenTeflon-coated surgical steel is used, a compatible fixation method mustbe employed. For example, the Teflon coating may be first scraped awayin the regions of abutment between the two components before the joiningstep is carried out, or a special purpose adhesive may be used.Preferably, however, the Teflon coating is more practically appliedafter the two-piece structure has been fabricated.

[0074] The resulting two-piece (plus supplementary and/or minor struts)guided-tissue regeneration plate 49 shown in FIG. 21 can then be used inthe process described above with notably improved results with respectto the speed and quality with which jaw bone is regenerated along apatient's bony ridge and thicker and more healthy overlying periosteum.Consequently, the long term outlook for the integrity of subsequentdental implants is correspondingly improved, a more satisfactory resulthaving been obtained more quickly.

[0075] In order to insure a secure fixation of the two-pieceguided-tissue regeneration plate 49 to the support structure which isfixed to the jaw bone of a patient as previously described with respectto the guided-tissue regeneration plates 30, 35, it may be useful tolocally reinforce the central inner support ring 43 which defines thecentral aperture 44 which functionally corresponds to the apertures 31,25. FIGS. 22 and 23 illustrate a reinforced central inner support ring43. More particularly, as best shown in the enlarged fragmentary crosssection of FIG. 23, the thickness of the central inner support ring 43may be augmented by any suitable means such as by stacking additionalmaterial 43A over the support ring 43 which is integral with the struts42 as previously described.

[0076] Preparation of a variant version of the second preferredembodiment is illustrated in FIGS. 24-27. FIG. 24 shows an imperforatemonolithic plate 60 having peripheral outer dimensions corresponding tothose of the guided-tissue regeneration plate 49 shown in FIG. 22. Aspreviously mentioned, a preferred material is titanium plate having athickness of about 0.008-0.025 of an inch and preferably about 0.012 ofan inch. The imperforate plate 60 is subjected to further processing toobtain the desired guided-tissue regeneration plate as a unitarystructure.

[0077] Thus, referring now to FIG. 25, in anticipation of reducing thethickness of predetermined central regions of the plate 60, a suitableconfigured mask 61 is prepared and juxtaposed overlaying one surface ofthe plate. The mask 61 may be a separate stencil-like layer or may bedeposited directly on the surface of the plate 60 by a conventionaltechnique such as by depositing a photo-resist layer applied in thedesired pattern; i.e., a pattern which will shield the areas of theplate 60 which are not to be reduced in thickness. Accordingly, theareas which are not coated or otherwise masked off are subject toreduction in thickness. Because the open region pattern employed in theexample describing the first version of the second preferred embodimentof the guided-tissue regeneration plate has been found to work well, itis also used to describe the second version. Still referring to FIG. 25,radial struts 64 of the mask 61 define a series of circumferentiallydistributed openings 62 while arms adjoining adjacent radial struts 64define supplementary struts 65 which corresponds to the supplementarystruts 48 shown in FIGS. 19, 21 and 22 and discussed above. Therectangular configuration of the supplementary struts 65 and the innerends of the radial struts 64 define additional openings 67. The innerends of the radial struts 64 each terminate at a ring 66 whichcircumscribes central mask opening 63.

[0078] Once the mask 61 has been emplaced over the plate 60, the maskedsurface can be subjected to a conventional acid etch to removeunprotected metal and hence reduce the thickness of the plate 60 in theunmasked areas to the previously discussed range of 0.002-0.006 of aninch and preferably about 0.003 of an inch. The rate and extent of themetal removal can be controlled, as well known in the art, by selectingthe type of acid, its concentration and temperature and the length oftime the plate is subjected to the acid.

[0079]FIG. 26 shows the plate 60A after the acid etch step has beencompleted. Thus, regions 68, 69, 70 will be understood to be ofdiminished thickness while the strut regions 71, supplementary strutregions 72, central ring region 73 and peripheral region 74 remain atthe original thickness of the plate because they were protected by themask during the etching operation.

[0080] The second variant of the second preferred embodiment of theguided-tissue regeneration plate is competed by perforating its surfacewith a large number of closely spaced apertures, typically circular inshape. As shown in FIG. 27, the guided-tissue regeneration plate 60B hasbeen pierced by numerous closely spaced apertures 75 in the regions 71,72, 73, 74 of the plate which were not reduced in thickness. In theregions 68, 69 which were reduced in thickness, the plate is piercedeven more densely with numerous closely spaced apertures 76. The centralaperture 70 is opened through the plate 60B during the finishing processto serve as a fixation screw receiving opening in the same manner aspreviously described with respect to the central aperture 44 (FIGS. 22,23) of the two-piece first variant of the alternative preferredembodiment for the guided-tissue regeneration plate.

[0081] The size and spacing of the apertures in both the originalthickness and the reduced thickness regions of the guided-tissueregeneration plate 60B affects both the porosity and the mechanicalpliability of the individual regions. The spacing can be either randomas shown for the majority of the areas in FIG. 27 or in a definitepattern as shown in the regions 76 (a thinned-down region) and 77 (anoriginal thickness region—not enlarged). The regions 76 and 77 arecontrasted by the use of smaller apertures and finer spacing in thereduced thickness region 76, thus achieving increased porosity. Incontrast, the larger apertures and wider spacing employed in theoriginal thickness region 77 provides a stiffer, but still compliant,structure for the peripheral region 74 which achieves a structuremechanically well-adapted for emplacement and subsequent maintenance ofits position and configuration in use.

[0082] It was noted above that one or more minor struts (e.g., the minorstruts 46, 47 shown in FIGS. 19, 21) may be provided as necessary toensure sufficient rigidity to the screened portion of the first variantof the alternative preferred embodiment for the guided-tissueregeneration plate. Corresponding minor struts may also be incorporatedinto the second variant of the alternative preferred embodiment for theguided-tissue regeneration plate shown in FIG. 27 by either makingprovision for such in the mask 61 or by later affixing them, as separatecomponents in the manner previously described, to the unitary structure.

[0083] While the presently preferred material for either version of thealternative preferred embodiment is titanium, the use of othermaterials, non-resorptive and resorptive, as discussed above may beemployed. As with the previously described embodiments, after thedesired bone regeneration has been achieved, the variant preferredembodiment of the guided-tissue regeneration plate may be left in placeor removed prior to the implantation process as may be appropriate for agiven patient. Further, as also previously described with respect to theguided-tissue regeneration plate 35, if a temporary period of isolationfrom epithelial cells is desired to create a membrane barrier fromepithelial cells for a limited period of time which allows for theexchange of nutrients, ions, and tissue fluid or perhaps blood supply,then a resorptive barrier such as Vicryl™, collagen, resorptivehydroxyapatite crystals or Guidor™ can be applied to the top or bottomside of the guided-tissue regeneration plates 49, 60B to seal theperforations, then resorbing a limited time later after the system isinstalled.

[0084] A performance improving enhancement which can be employed eitherwith the guided-tissue regeneration plate described and claimed in theaforementioned parent U.S. Pat. No. 5,839,899 or with the guided-tissueregeneration plates described and claimed herein is to decrease thesurface tension, and hence increase the “wetability”, of theguided-tissue regeneration plate surfaces. This effect can be achievedin several ways. For example, subjecting the guided-tissue regenerationplate to a plasma spray or gently blasting it with fine to coarse gritabrasive or subjecting it to a suitable acid etchant for a suitableperiod will achieve the desired result. This slight roughening of thesurface of the guided-tissue regeneration plate serves to promote bettertissue adhesion and consequently decreases susceptibility to infectionor exposure of the plate. In a variant of this enhancement, only the top(tissue side) of the guided-tissue regeneration plate is roughened inorder that the tissue will adhere to it, yet the plate can be readilypeeled away in due course from the underlying, newly-formed bone.

[0085] Thus, while the principles of the invention have now been madeclear in an illustrative embodiment, there will be immediately obviousto those skilled in the art many modifications of structure,arrangements, proportions, the elements, materials, and components, usedin the practice of the invention which are particularly adapted forspecific environments and operating requirements without departing fromthose principles.

What is claimed is:
 1. In apparatus for use in a method of growing bonein order to increase the volume of the bony ridge of the maxilla ormandible by creating a protected and supported space between theunderside of the gum tissue and the jaw bone which is protected fromoutside chewing forces, muscular or tissue pressure, or any otherpremature loading by utilizing a guided-tissue regeneration platesupport and fixation system, which method comprises: A) fixing a supportmedium to the jaw bone, said support medium being configured to receiveand support a guided-tissue regeneration plate; B) juxtaposing aguided-tissue regeneration plate with respect to the jaw bone in atent-like manner to create a protected space by affixing saidguided-tissue regeneration plate to and suspending it from said supportmedium, which said guided-tissue regeneration plate is pliable andmoldable, but keeps its shape after being molded, said guided-tissueregeneration plate being further characterized in that it is fabricatedfrom a bio-compatible material; and C) waiting for bone to grow in theresulting protected space; the improvement in which: D) saidguided-tissue regeneration plate comprises first and second integratedcomponents including: 1) a first component comprising a support platehaving a peripheral region and a generally open central portion; and 2)a fine mesh screen juxtaposed over said central portion of said supportplate and fixed to said peripheral region thereof.
 2. The apparatus ofclaim 1 in which said support plate and said fine mesh screen are eachmade of a bio-compatible material selected from the group includingtitanium, chromium cobalt alloy and Teflon-coated surgical steel and inwhich said peripheral region of said support plate is perforated.
 3. Theapparatus of claim 1 in which said guided-tissue regeneration plate iscoated with a resorptive, bio-compatible material for the purpose ofcreating a temporary guided-tissue regeneration plate barrier to preventmigration of epithelial cells across its surface, yet allow blood supplyand/or nutrients to pass through the resorptive barrier.
 4. Theapparatus of claim 2 in which said guided-tissue regeneration plate iscoated with a resorptive, bio-compatible material for the purpose ofcreating a temporary guided-tissue regeneration plate barrier to preventmigration of epithelial cells across its surface, yet allow blood supplyand/or nutrients to pass through the resorptive barrier.
 5. Theapparatus of claim 1 in which: A) the thickness of said peripheralregion of said support plate falls within the range of 0.008-0.025 of aninch; and B) said fine mesh screen comprises a weave of wire inwhich: 1) the diameter said wire employed falls within the range of0.002-0.006 of an inch; and 2) the weave of said wire falls within therange of 10×10 wires per inch to 200×200 wires per inch.
 6. Theapparatus of claim 2 in which: A) the thickness of said peripheralregion of said support plate falls within the range of 0.008-0.025 of aninch; and B) said fine mesh screen comprises a weave of wire inwhich: 1) the diameter said wire employed falls within the range of0.002-0.006 of an inch; and 2) the weave of said wire falls within therange of 10×10 wires per inch to 200×200 wires per inch.
 7. Theapparatus of claim 3 in which: A) the thickness of said peripheralregion of said support plate falls within the range of 0.008-0.025 of aninch; and B) said fine mesh screen comprises a weave of wire inwhich: 1) the diameter said wire employed falls within the range of0.002-0.006 of an inch; and 2) the weave of said wire falls within therange of 10×10 wires per inch to 75×75 wires per inch.
 8. The apparatusof claim 4 in which: A) the thickness of said peripheral region of saidsupport plate falls within the range of 0.008-0.025 of an inch; and B)said fine mesh screen comprises a weave of wire in which: 1) thediameter said wire employed falls within the range of 0.002-0.006 of aninch; and 2) the weave of said wire falls within the range of 10×10wires per inch to 200×200 wires per inch.
 9. The apparatus of claim 1 inwhich integral struts extend from said peripheral region of said supportplate into said generally open central portion thereof to providesupport for said fine mesh screen.
 10. The apparatus of claim 2 in whichintegral struts extend from said peripheral region of said support plateinto said generally open central portion thereof to provide support forsaid fine mesh screen.
 11. The apparatus of claim 5 in which integralstruts extend from said peripheral region of said support plate intosaid generally open central portion thereof to provide support for saidfine mesh screen.
 12. The apparatus of claim 6 in which integral strutsextend from said peripheral region of said support plate into saidgenerally open central portion thereof to provide support for said finemesh screen.
 13. The apparatus of claim 1 in which at least a pluralityof said integral struts join a circular central support having anaperture therethrough for coupling with said support medium.
 14. Theapparatus of claim 2 in which at least a plurality of said integralstruts join a circular central support having an aperture therethroughfor coupling with said support medium.
 15. The apparatus of claim 5 inwhich at least a plurality of said integral struts join a circularcentral support having an aperture therethrough for coupling with saidsupport medium.
 16. The apparatus of claim 6 in which at least aplurality of said integral struts join a circular central support havingan aperture therethrough for coupling with said support medium.
 17. Theapparatus of claim 9 in which at least a plurality of said integralstruts join a circular central support having an aperture therethroughfor coupling with said support medium.
 18. The apparatus of claim 10 inwhich at least a plurality of said integral struts join a circularcentral support having an aperture therethrough for coupling with saidsupport medium.
 19. The apparatus of claim 11 in which at least aplurality of said integral struts join a circular central support havingan aperture therethrough for coupling with said support medium.
 20. Theapparatus of claim 12 in which at least a plurality of said integralstruts join a circular central support having an aperture therethroughfor coupling with said support medium.
 21. In apparatus for use in amethod of growing bone in order to increase the volume of the bony ridgeof the maxilla or mandible by creating a protected and supported spacebetween the underside of the gum tissue and the jaw bone which isprotected from outside chewing forces, muscular or tissue pressure, orany other premature loading by utilizing a guided-tissue regenerationplate support and fixation system, which method comprises: A) fixing asupport medium to the jaw bone, said support medium being configured toreceive and support a guided-tissue regeneration plate; B) juxtaposing aguided-tissue regeneration plate with respect to the jaw bone in atent-like manner to create a protected space by affixing saidguided-tissue regeneration plate to and suspending it from said supportmedium, which said guided-tissue regeneration plate is pliable andmoldable, but keeps its shape after being molded, said guided-tissueregeneration plate being further characterized in that it is fabricatedfrom a bio-compatible material; and C) waiting for bone to grow in theresulting protected space; the improvement in which: D) saidguided-tissue regeneration plate comprises first and second regions of amonolithic structure: 1) said first region comprising a peripheral areahaving a first thickness; and 2) said second region comprising a centralarea having a thickness which is less than that of said peripheralregion, said central area being perforated with a plurality ofapertures.
 22. The apparatus of claim 21 in which said monolithicstructure is made of a bio-compatible material selected from the groupincluding titanium, chromium cobalt alloy and Teflon-coated surgicalsteel and in which said peripheral region of said support plate isperforated.
 23. The apparatus of claim 21 in which said guided-tissueregeneration plate is coated with a resorptive, bio-compatible materialfor the purpose of creating a temporary guided-tissue regeneration platebarrier to prevent migration of epithelial cells across its surface, yetallow blood supply and/or nutrients to pass through the resorptivebarrier.
 24. The apparatus of claim 21 in which said guided-tissueregeneration plate is coated with a resorptive, bio-compatible materialfor the purpose of creating a temporary guided-tissue regeneration platebarrier to prevent migration of epithelial cells across its surface, yetallow blood supply and/or nutrients to pass through the resorptivebarrier.
 25. The apparatus of claim 21 in which: A) the thickness ofsaid peripheral area of said guided-tissue regeneration plate fallswithin the range of 0.008-0.025 of an inch; and B) the thickness of saidcentral area of said guided-tissue regeneration plate falls within therange of 0.002-0.006 of an inch.
 26. The apparatus of claim 22 in which:A) the thickness of said peripheral area of said guided-tissueregeneration plate falls within the range of 0.008-0.025 of an inch; andB) the thickness of said central area of said guided-tissue regenerationplate falls within the range of 0.002-0.006 of an inch.
 27. Theapparatus of claim 21 in which integral struts extend from saidperipheral area of said guided-tissue regeneration plate into saidcentral area to provide support for said central area.
 28. The apparatusof claim 22 in which integral struts extend from said peripheral area ofsaid guided-tissue regeneration plate into said central area to providesupport for said central area.
 29. The apparatus of claim 25 in whichintegral struts extend from said peripheral area of said guided-tissueregeneration plate into said central area to provide support for saidcentral area.
 30. The apparatus of claim 26 in which integral strutsextend from said peripheral area of said guided-tissue regenerationplate into said central area to provide support for said central area.31. The apparatus of claim 21 in which at least a plurality of saidintegral struts join a circular central support having an aperturetherethrough for coupling with said support medium.
 32. The apparatus ofclaim 22 in which at least a plurality of said integral struts join acircular central support having an aperture therethrough for couplingwith said support medium.
 33. The apparatus of claim 25 in which atleast a plurality of said integral struts join a circular centralsupport having an aperture therethrough for coupling with said supportmedium.
 34. The apparatus of claim 26 in which at least a plurality ofsaid integral struts join a circular central support having an aperturetherethrough for coupling with said support medium.
 35. The apparatus ofclaim 27 in which at least a plurality of said integral struts join acircular central support having an aperture therethrough for couplingwith said support medium.
 36. The apparatus of claim 28 in which atleast a plurality of said integral struts join a circular centralsupport having an aperture therethrough for coupling with said supportmedium.
 37. The apparatus of claim 29 in which at least a plurality ofsaid integral struts join a circular central support having an aperturetherethrough for coupling with said support medium.
 38. The apparatus ofclaim 30 in which at least a plurality of said integral struts join acircular central support having an aperture therethrough for couplingwith said support medium.
 39. The apparatus of claim 21 in which saidguided-tissue regeneration plate is fabricated by the steps of: A)overlaying, on a first surface of a monolithic plate, a mask conformingto the shape of said peripheral area such that only an area conformingto the shape of the central area is exposed; B) etching the firstsurface of the monolithic plate in the exposed area to diminish thethickness of the monolithic plate in the exposed area; and C)perforating the central area with a plurality of apertures.
 40. Theapparatus of claim 39 in which the monolithic plate is a titanium plate.41. In apparatus for use in a method of growing bone in order toincrease the volume of the bony ridge of the maxilla or mandible bycreating a protected and supported space between the underside of thegum tissue and the jaw bone which is protected from outside chewingforces, muscular or tissue pressure, or any other premature loading byutilizing a guided-tissue regeneration plate support and fixationsystem, which method comprises: A) juxtaposing a guided-tissueregeneration plate with respect to the jaw bone in a tent-like manner tocreate a protected space, which said guided-tissue regeneration plate ispliable and moldable, but keeps its shape after being molded, saidguided-tissue regeneration plate being further characterized in that itis fabricated from a bio-compatible material; and B) waiting for bone togrow in the resulting protected space; the improvement in which: C) atleast a first region of the surface of said guided-tissue regenerationplate is roughened to decrease the surface tension thereof.
 42. Theapparatus of claim 41 in which the entire surface of said guided-tissueregeneration plate is roughened to decrease the surface tension thereof.